<本来想水一水，结果听取wa声一片>

#include <bits/stdc++.h>

using namespace std;

#define ll unsigned long long int

queue<ll> dat;
int main()
{
    ios::sync_with_stdio(false);
    queue<ll> dat;
    int n = 0;
    cin >> n;
    while (n--)
    {
        ll op = 0, x;
        cin >> op;
        switch (op)
        {
        case 1:
            cin >> x;
            dat.push(x);
            break;
        case 2:
            if (dat.empty())
            {
                cout << "ERR_CANNOT_POP" << endl;
            }
            else
            {
                dat.pop();
            }
            break;
        case 3:
            if (dat.empty())
            {
                cout << "ERR_CONNOT_QUERY" << endl;
            }
            else
            {
                cout << dat.front() << endl;
            }
            break;
        case 4:
            cout << dat.size() << endl;
            break;
        default:
            break;
        }
    }
    return 0;
}